CODEWITHSUNDEEP
iphoneobjective-ccocoa-touchios5memory-management
JacobS
JacobS

Reputation: 31

Memory management creating an NSDictionary with NSMutableArrays

I'm having problem understanding memory management when creating a dictionary with mutable arrays. I'm using the ios6 SDK with deployment target 5.1.

In the implementation of the class "Group" the method "namesAndEmails" builds an array "emails" that contains the emails addresses for Person objects with an email. If the Person object does not have an email the Person name is added to another array "namesWithNoEmail". The arrays are returned in a dictionary.

#import "Group.h"
@implementation Group 

-(NSDictionary*) namesAndEmails {
    NSMutableArray  *emails = [[NSMutableArray alloc] initWithCapacity:0] ;
    NSMutableArray  *namesWithNoEmail = [[NSMutableArray alloc] initWithCapacity:0];
    NSString *email;
    NSString *name;
    for (Person *p in allPersons) {
        email = p.email;
        name = p.name;
        if ([email length]==0) {
            [namesWithNoEmail addObject:name];
        } else {
            [emails addObject:email];
        }
    }
    NSArray *keys = [NSArray arrayWithObjects:@"emails",@"names", nil];
    NSArray *objects = [NSArray arrayWithObjects:emails, namesWithNoEmail, nil];
    //[emails release];
    //[namesWithNoEmail release];

     return [NSDictionary dictionaryWithObjects:objects forKeys:keys];
}

Somewhere else in the code I wish to send an email to a group of people so I call the emailGroup method which gets a dictionary out by calling "namesAndEmails" on the group.

-(void) emailGroup:(Group*) g {

    NSDictionary *emailInfo = [g namesAndEmails];
    guestsWithNoEmail = [emailInfo objectForKey:@"names"];
    guestEmails = [emailInfo objectForKey:@"emails"];

   int nGuestsWithNoEmail = [guestsWithNoEmail count];

   if (nGuestsWithNoEmail > 0) {
      UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"No emails" message:@"" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease];
      [alert show];
   }

    // some more code here


    MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
    picker.mailComposeDelegate = self;
    [picker setSubject:subject];
    [picker setMessageBody:@"" isHTML:NO];
    [picker setToRecipients:guestEmails];
    [[self delegate ] presentModalViewController:picker animated:YES];
    [picker release];
}

As far as I understand [NSDictionary dictionaryWithObjects:objects forKeys:keys] in "namesAndEmails" returns an autoreleased dictionary. But why does my code crash if I release the "emails" and "namesWithNoEmail" arrays? I thought that the dictionary would have ownership of the array after they are added and therefore it would be safe to release the arrays in the method. I guess that's not correct, but why?

Is the a more clean way of doing this? Thank you for any advice!

Upvotes: 2

Views: 296

Answers (1)

DBD
DBD

Reputation: 23233

My first suggestion would be to use the "Product->Analyze" feature. If you leaking or over releasing somewhere, it will probably give you the exact chain of events.

Secondly, I can't see the linking between your methods nameAndEmails and emailGroup:. Because I can't see the connection, I can't tell you if the autorelease is causing the problem.

Autoreleased objects get released when the the main run loop cycles. So it's very possible your NSDictionary is getting released. You could test this by doing anything from setting the memory location as a "watch" in the debugger to putting printing something in the console lines each time the runloop your in cycles (I made the assumption your in the main run loop, so correct me if that's not true).

Other things you can do to track the problem would be to use "Zombies" in instruments or NSZombieEnable=YES in your configuration

Upvotes: 2

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